LAYERING ZIRCONIA WITH COMPOSITE OR PORCELAIN? AN ANALYSIS OF FRACTURE RESISTANCE

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1 Original Article LAYERING ZIRCONIA WITH COMPOSITE OR PORCELAIN? AN ANALYSIS OF FRACTURE RESISTANCE Naveen Oberoi Professor, Dept. of Prosthodontics, BJS Dental College, Ludhiana Abstract Introduction:Porcelain layered zirconia restorations are aesthetic but have an essential drawback associated of chipping and difficult repair. Indirect composites, on the other hand, when layered have shown higher mean longevity compared to metal-ceramics The present study was carried out to evaluate the fracture resistance of composite layered zirconia crowns compared to porcelain layered zirconia crowns using fracture resistance analysis. Materials and Methods: Zirconia substructures were fabricated and divided into two groups. A static load was applied and the load was recorded until fracture.results: Fracture resistance of composite layered zirconia crowns show comparable results to that of porcelain veneered zirconia crowns (p=0.628). Conclusion: Composite layering can withstand high occlusal loads similar to the porcelain veneered zirconia crowns with no significant difference with the added advantage of easy and less damaging cohesive repair. Keywords: Zirconia, Composite veneer, Porcelain veneer, Bi-layered crowns, Fracture resistance Corrseponding Author:Dr. Naveen Oberoi,Professor, Dept. of Prosthodontics, BJS Dental College, Ludhiana. How to cite: Oberoi N.Layering Zirconia with Composite or Porcelain? An Analysis of Fracture Resistance. IDA Lud J le Dent 2017;1(3):8-12. INTRODUCTION Restoration of teeth using all-ceramic full crown restorations usually involves using a strong substructure like zirconia that is layered with feldspathic porcelain. Studies have shown that the final restoration provides excellent aesthetics; however, they are quite liable to chipping 1. Porcelains are not able to bear high tensile stresses that lead tofracture 2 and are also abrasive which can lead to wearing off of the opposing teeth 3. For improving onto such issues, we need to mend coefficient of thermal expansion (CTE) match between the IDA Ludhiana s Journal ledentistryvol.1 issue

2 layering material and the substructure 4 and firing period while buildup 5. It has been previously proven that chipping of ceramic veneer occurs with higher frequency in a zirconia substructure than with metal 6. A substitute to be consideredcan be layering zirconia with composite. Composites are used as direct restorativesbecause of their brilliant optical andmechanical properties;their ease of handling and the micro - mechanical bonding 7. It was shown in a study that composite layered onto metal crowns shows a higher mean longevity when compared to metal-ceramics. Thus, the present study aimed to evaluate whether layering with composite would also have a similar effect with a zirconia substructure or not. MATERIALS AND METHODS Zirconia substructures were made using CEREC CAD/CAM system (CEREC inlab, Sirona Dental Systems, Germany). A zirconia substructure (0.7 mm thick) was designed. The substructure was milled using zirconia blocks (InCeram YZ, VITA Germany) and after that it was sintered using the manufacturer s instructions. The obtained substructures were divided into two groups of 10 blocks each depending on the layering material to be used into: zirconia layered with composite YZ/LC (VM LC, Vita) and zirconia/porcelain YZ/VM9 (VM9, Vita).For layering of composite, a composite veneer was light cured after sandblasting the substructure and coating it with a using universal primer (Single Bond Universal, 3M ESPE, St. Paul, MN, USA). For porcelain, the substructures were fired using the regular manufacturer s instructions. Crowns were then finished and polished to achieve a standard clinical thickness of 1.2 mm. The crowns were then cemented before being subjected to compressive load.a universal testing machine (Lloyd, Lloyd Instruments, UK) was used for applying a load via a steel ball indenter at a crosshead speed of 1 mm/min in the middle of the crown on the occlusal surface. The maximum load causing failure was recorded.the results thereby obtained were compared using ANOVA followed by Post Hoc Tukey s test at significance level of p<0.05 using SPSS version 23.0 (IBM Co., NY, USA). RESULTS The mean fracture resistance of zirconia crowns layered with composite was found to be 1321±220MPa. For the other group, where zirconia crowns were layered with porcelain, a slightly higher fracture resistance was observed[1387±176 MPa]. However, the difference was found to be statistically non significant (p= 0.628). DISCUSSION Zirconia crowns have added a new flourishing tool into the hands of dentists. Porcelain layering over the zirconia substructure provides for the translucency over the otherwise opaque lifeless zirconia. But this comes with its own inherent problems of abrasion and chipping under loads primarily due to a mismatched coefficient of thermal expansion.in the present study, composite was anticipated to overcome these drawbacks. For such crowns, indirect light cured composite is layered over the zirconia substructure. The present system has associated benefits that include biocompatibility, retains the strength of the zirconia substructure and a lesser abrasive composite veneer that protects the opposing teeth and also facilitates intra-oral repair. Many studies have tried to evaluate and compare the properties of zirconia and composites 8,9, however, only a few studies have tested the performance of both being used simultaneously as a system 10.It is a well-known fact that the results that are IDA Ludhiana s Journal ledentistryvol.1 issue

3 obtained from in-vitro lab tests cannot be directly applied to the oral cavity as the direction of forces as well as its amplitude varies. Also, it depends on the kind of material being subjected to the load apart from the thermal variations.but still, such tests help us get an idea into the comparison of certain materials and can help predict their behaviour in the oral environment in comparison to the standards.in the present study, it was seen that composite layered crowns fractured at a mean load of 1321MPawhen compared to 1387MPa for the porcelain veneered zirconia substructures. This is in accordance with various other studies that have concluded that the indirect composite layered onto zirconia crowns show equivalent fracture resistance when compared to the porcelain layering 10,11. Bite forces recorded inside the oral cavity are a little lesser 2 ( MPa) than the forces such crown systems can bear as used in the present study. Fracture resistance of yttriumstabilized zirconium oxide substructures layerd with feldspathic ceramics in the past have given comparable results to the present study. In a test, VM9 feldspathic porcelain gave an average fracture resistance of 1459 N ±492MPa 12.The authors in this study compared porcelain layered crowns with porcelain crowns (VITA mark II, Vita Zahnfabrik) and obtained an average resistance of 1270 ±10 MPa.Hence, it can be seen that the composite veneered zirconia crowns withstood higher loads than VITA mark II crowns.sorrentino et al assessed monolithic zirconia molar crowns with 1.5 and 1.0 mm thickness and found them capable of bearing fracture load of 1554± 366 MPa and 1655 ± 314 MPa respectively 13. Theseresults when compared with the present study show that composite layered onto zirconia crowns showscomparable results to purely zirconia based crowns. For an intra-oral repair of a cohesively fractured ceramic crown, composite can be considered asa cost effective method with the benefit of maintenance of the restoration substructure and thereby protecting the underlying tooth from unnecessary forces for aesthetics 14. If the results of our study are to be seen, then restoring a fractured composite veneer intraorally a similar material would give more optimal esthetics as well as be less tedious when restored with the same material.supplementary testing for the present studies is required under situations simulating the oral environment, e.g. thermocycling and by using bite simulators, before such results can be deliberated for clinical application. CONCLUSIONS The results of the present study conclude that crowns fabricated using a zirconia coping and layered with indirect composite gave similar results to porcelain veneered zirconia crowns with no statistically significant difference (p = 0.628). REFERENCES 1. Guess PC, Zavanelli RA, Silva NRFA, Bonfante EA, Coelho PG, Thompson VP. Monolithic CAD/CAM lithium disilicate versus veneered Y-TZP crowns: comparison of failure modes and reliability after fatigue. Int J Prosthodont 2010; 23: Casson AM, Glyn Jones JC, Youngson CC, Wood DJ. The effect of luting media on the fracture resistance of a flame sprayed all-ceramic crown. J Dent 2001; 29: Hudson JD, Goldstein GR, Georgescu M. Enamel wear caused by three different restorative materials. J Prosthet Dent 1995; 74: Fischer J, Stawarzcyk B, Trottmann A, Hammerle CH. Impact of thermal misfit on shear strength of veneering IDA Ludhiana s Journal ledentistryvol.1 issue

4 ceramic/zirconia composites. Dent Mater 2009; 25: Rues S, Kroger E, Muller D, Schmitter M. Effect of firing protocols on cohesive failure of all-ceramic crowns. J Dent 2010; 38: Sailer I, Pjetursson BE, Zwahlen M, Hammerle CHF. A systematic review of the survival and complication rates of all-ceramic and metal-ceramic reconstructions after an observation period of at least 3 years. Part II: fixed dental prostheses. Clin Oral Implants Res 2007; 18: Hervas-Garcia A, Martinez-Lozano MA, Cabanes-Vila J, Barjau-Escribano A, Fos-Galve P. Composite resins. A review of the materials and clinical indications. Med Oral Patol Oral Cir Bucal 2006; 11: Guazzato M, Albakry M, Ringer SP, Swain MV. Strength, fracture toughness and microstructure of a selection of allceramic materials. Part II. Zirconiabased dental ceramics. Dent Mater 2004; 20: Manicone PF, Rossi Iommetti P, Raffaelli L. An overview of zirconia ceramics: basic properties and clinical applications. J Dent 2007; 35: Taguchi K, Komine F, Fushiki R, Blatz MB, Kamio S, Matsumura H. Fracture Conflict of Interest:NoneSource of Support: NiL resistance of single-tooth implantsupported zirconia-based indirect composite-layered molar restorations. Clin Oral Implants Res 2014; 25: Komine F, Taguchi K, Fushiki R, Kamio S, Iwasaki T, Matsumura H. In vitro comparison of fracture load of implantsupported, zirconia-based, porcelainand composite layered restorations after artificial aging. Dent Mater J 2014; 33: Zahran M, El-Mowafy O, Tam L, Watson PA, Finer Y. Fracture strength and fatigue resistance of all-ceramic molar crowns manufactured with CAD/CAM technology. J Prosthodont 2008; 17: Sorrentino R, Triulzio C, Tricarico MG, Bonadeo G, Gherlone EF, Ferrari M. In vitro analysis of the fracture resistance of CAD-CAM monolithic zirconia molar crowns with different occlusal thickness. J Mech Behav Biomed Mater 2016; 61: Han IH, Kang DW, Chung CH, Choe HC, Son MK. Effect of various intraoral repair systems on the shear bond strength of composite resin to zirconia. J Adv Prosthodont 2013; 5: This work is licensed under a Creative Commons Attribution 4.0 International License IDA Ludhiana s Journal ledentistryvol.1 issue

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